Tubular preparation of thermoplastic film

ABSTRACT

IN A CONTINUOUS PROCESS FOR PRODUCING AN ORIENTED THERMOPLASTIC FILM COMPRISING EXTRUDING A THERMOPLASTIC MATERIAL IN ITS FORMATIVE STATE INTO THE FORM OF A TUBE, QUENCHING THE TUBE TO A TEMPERATURE BELOW ITS FORMATIVE STATE, REHEATING THE TUBE TO A TEMPATURE WITHIN ITS ORIENTATION TEMPERATURE RANGE, EXPANDING THE TUBE AND THEREAFTER COLLAPSING AND COLLECTING THE TUBE, THE IMPROVEMENT WHICH COMPRISES OSCILLATING THE TUBE ABOUT ITS AXIS BY APPLYING ROTATIONAL TORQUE TO THE TUBE AFTER QUENCHING AND BEFORE REHEATING TO DISTRIBUTE GUAGE IRREGULARITIES ABOUT THE CIRCUMFERENCE OF THE TUBE. IT IS PREFERRED THAT THE TUBE BE OSCILLATED THROUGH A ROTATIONAL CYCLE OF 180* AT A ROTATIONAL SPEED OF V/2D WHEREIN V IS THE LINEAR SPEED OF THE TUBE BEING EXTRUDED AND D IS THE DISTANCE BETWEEN THE EXTRUSION DIE AND THE REGION OF INITIAL ORIENTATION EXPANSION TO DISTRIBUTE GUAGE IRREGULARITIES THROUGHOUT THE FULL CIRCUMFERENCE OF THE TUBE. OSCILLATION OF THE TUBE IS ACCOMPLISHED BY ROTATION OF A TUBE ADVANCER COMPRISING A PLURALITY OF IDLER ROLLS CIRCULARLY DISPOSED AROUND THE INTERNAL WALL OF THE QUENCHED TUBE AND A PLURALITY OF DRIVEN ROLLS IN COOPERATIVE ARRANGEMENT WITH THE IDLER ROLLS CIRCUMFERENTIALLY POSITIONED IMMEDIATELY EXTERIOR TO THE TUBE, THE IDLER ROLLS AND THE DRIVEN ROLLS EACH BEING MOUNTED ON ROTATABLE FRAMES.

DEFENSIVE PUBLICATION UNITED STATES PATENT OFFICE Published at therequest of the applicant or owner in accordance with the Notice of Dec.16, 1969, 869 0.6. 687. The abstracts of Defensive Publicationapplications are identified by distinctly numbered series and arearranged chronologically. The heading of each abstract indicates thenumber of pages of specification, including claims and sheets ofdrawings contained in the application as originally filed. The files ofthese applications are available to the public for inspection andreproduction may be purchased for 30 cents a sheet.

Defensive Publication applications have not been examined as to themerits of alleged invention. The Patent Ofiice makes no assertion as tothe novelty of the disclosed subject matter.

PUBLISHED JUNE 26, 1973 T911,016 TUBULAR PREPARATION OF THERMOPLASTICFILM Edward J. Moore, Florence, S.C., assignor to E. I. du Pont deNernours and Company, Wilmington, Del.

Continuation of abandoned application Ser. No. 36,034,

May 11, 1970. This application Mar. 30, 1972, Ser.

Int. Cl. B29c 5/04, 23/00; 182% 9/24 2 Sheets Drawing. 3 PagesSpecification In a continuous process for producing an orientedthermoplastic film comprising extruding a thermoplastic material in itsformative state into the form of a tube, quenching the tube to atemperature below its formative state, reheating the tube to atemperature within its orientation temperature range, expanding the tubeand there after collapsing and collecting the tube, the improvementwhich comprises oscillating the tube about its axis by applyingrotational torque to the tube after quenching and before reheating todistribute gauge irregularities about the circumference of the tube.

It is preferred that the tube be oscillated through a rotational cycleof 180 at a rotational speed of v/Zd wherein v is the linear speed ofthe tube being extruded and d is the distance between the extrusion dieand the region of initial orientation expansion to distribute gaugeirregularities throughout the full circumference of the tube.

Oscillation of the tube is accomplished by rotation of a tube advancercomprising a plurality of idler rolls circularly disposed around theinternal wall of the quenched tube and a plurality of driven rolls incooperative arrangement with the idler rolls circumferentiallypositioned immediately exterior to the tube, the idler rolls and thedriven rolls each being mounted on rotatable frames.

June 26, 1973 E. J. MOORE TUBULAR PREPARATION 01" THERMOPLASTIC PHIM 2Sheets-Shea t 1 Original Filed m 11, 1970 3W9 QNIGNVIS (1i SNIIHVISEISVS SNIGNVIS 'IVHGISHH INVENTOR MOORE EDWARD J.

T9ll,016

June 26, 1973 E. J MOORE TUBULAR PREPARATION OI" THERMOPLASTIC FILM 2Sheets-Sheet.

Original Filed May 11, 1970

